Screw propeller for marine vessels



Feb. 25, 1930 A. J. MURRAY l SCREEN PROPELLER FOR MARINE. VESSELS `Fled Oct. l. 1924 m 5 INVENTOR l VATHOLE J. MURRAY, or' wESfi.` NEW BRIGHTON, NEW YORK; l'BEl'faTH-K- MRRAY Patented Feb. 25, `193() UNITED STATEs e EXECUTRIX on THE ESTATE E SAID yAfrrroLE J. MURRAY. iEcE'AsEDf vSCREW 'PROPELLER EoR' iu'ARiixE-VESSEIQSv 4 This invention'relatesito improvements inv .Screw propellers for marlne vessels.v

f One of the objects of this invention is to is to say, a larger propelling'powerlinprd portion to the unit of .power delivered to the shaft'th'an propellers heretofore used.

Another object of this invention is to produce apropeller which for a'given turning speed or angular velocity will be capable of Vtermedthe slip anglewth reference to a screw ,ipropellerof true screw design. 3 Another object of this invention is topro-Y f duce a'propeller whichwill operate efficiently 20. L y.Anotherobject of this invention is tov producey a'screw propeller, the yblades of which #will havegreat stiffness and rigidity.: L f Another'object ofthis invention v`is to -pro- {duce a screw propeller which .canbe usedto `Y`replace screwpropellers now .in useand when thus employed will afford greater economy -operatingeiiciently with 'an increased disc area orwith an increased aspectn'atiofithis term,l being employedto designate what 1s atihigh angular velocities. A g

' 'of. operationoversuch replaced propeller's by pelling thevessel at av similar speedwith: a

Y decreased expediture of horsepower,.or by producing av Simultaneous savingof .shaft V lless speed with greatlydiminished .horse powhorsepower andincrease in speed of propulsion,;v or by propelling the vessel atfslightly I. v er, or by propelling at a greatly increased speed vfor a smallA increase in shaft horse power. Y *v i l 1 Another object of this invention. 1s toproduce a screw propeller which lin its preferred embodiment will embody in itself ameans vfor Y. I i* ",preventingthe fluid which passes ythroughthe Y 'propeller .from having la rotating movement such as is incidental tothe kmovement vof vthe water'through ascrew propeller of truescrew form, thus eliminating any mechanism .eX-

sign'ed to prevent the rotationof the .race,"and 'also eliminating the cost'ofextraneousmechf Application-mea october 1e,` i924. serial No. 744,325. n

anismdesignedto redirect the-revolving race when rproduced and-so torecover vthe power lost in producing theaforesaid rotation of the Y l race.

Another object of vthis, invention is to producea screw propeller'of such form thatthe vwater vwill glide past the blades` without` appreciable loss of energy due to shock, and furthermore will attainthis result when all the .fluid Vmotions lare given due considerationfin the determination of the relative motions ofy the Screw-propeller blades and lthe passing water. i

Another object of my invention is to produce a screw'l propeller which will lcreate im'- proved lconditions for ymanoeuvring .or Steern Aing a vessel in water.

Another objectof my invention is to producean improved for'mrofy screw` propeller without increasing the cost of production'.vv

, With these and other objects `in View, the

plishment of the results herein contemplated,

- .and comprises' in. one of its adaptations the l .species or preferred form illustrated' inthe Ipropelling the vessel vat a greater speed .fora given unitof powerV at `the shaft, or prof .1

accompanying drawings, in which 1,-

Fig. l is a side orathwartship elevation of lone ofthe blades of a screwpropellerembodyi. ingmy inventionlincluding the bossl and'drivl ingshaft to which the boss is connected;

y Fig. 2 is an end view' of the'blade, boss cumferential strip. of the blade included 'bee' .tween imaginary cutting. cylinders-concentric 'with the driving Shaft;- and amechanical method of sweeping outor tracing the blade form shown inlfigs.` 1 to 3.

Referring now to these drawings whichv il- Y -lustrate a preferred yembodiment l of Vmyfinvention`, B indicatesfa blade'which maybe 19.0` .f Fig. 4 is adiagrammatic viewil-lustrating connected to the driving shaft-3 in any suitable mannerand may, if desired, be, formed integrally with. a boss 2vwhich5-as `s`hown`,1is

mounted on thedriving shaft and secured on said shaft by a nut 4. The boss, shaft and nut may have any of the conventional forms now in current practice. A single blade only is illustrated but it will be understood thaty the driving face of the blade from the leading edge to the following edge a substantially i concavo-convex surface, viz.,a surface which is substantially concave adjacentrto thevleading edge and convex 4adj acent toA the following edge, and in the preferred form of i'ny invention said blade face will have a substantially helicoidal curvature and theconcave surface and convex surface of said concave-convex surface will niergefwith each other at the center line of the blade, so that the driving surface of the blade at that side of said center line which extends to the leading edge will be concave while the driving surface of the blade fromsaid center line to the following edge will be substantially convex; vIn a blade having a driving face ofthe preferred form specified, a'l-lowance'will lbe made for the disposition of the blade thickness at the back of the blade,'and in the preferred embodiment of my inventionthe opposite or back surface of the blade will also f have the form above specified:

. In order more clearly to show and describe the preferred form of mypro'peller vblade,'fI have in Figs. l` arid 2 indicated by broken Alines 5 and 6 two imaginarycutting cylinders concentric with the shaftS, sosas to includebetween their intersections with thebladelsurface a circumferential blade'strip b', wliich, when projected into the `plaznjview. of Figr,

' will havesubstantially the concave-,convex form shown in said figure, lin which the arrow 9 will. indicate the fore-and-aftdirection of travel ofthe screw propeller relative-'tothe surrounding medium as the vessel and attached propeller arexprop'elled forwardv and the arrow 10 will indicate the instantaneous direction of motion of the propeller lbladef which is taken as rotating clockwise''or in 'the direction of the` arrow 110 in Fig; 2; Y

With these directionsof motions, 8 lindicates the end ofthe elementary strip the leading edge of the propeller `blade and 7 the end offsaid strip on the following edge of the propeller blade; Under conditions of uniform or steady motions offore-and-aft travel and rotation, these ends 7 and 8 of the Y circumferential strip will have spiral. motions each describing a helix-asindicated in said- Fig; 3 by the broken lines 11 and l2 respectively, and the 'formpor' .shapeof the circumferential strip b is preferably such that the edge or end 8 will be tangential with and merge into the helix l1 and the following end 7 will be tangential with and merge into the helix 12. The intermediate portion of the strip has a contraflexual lor*concave-(convex forin from the leading to the following edge giving an easy transition from the form at the leading end 0r edge to the form at the following end or edge.

It follows'fromthe' conditions above specified that thetwo helices traced by the ends or edges 7 and 8 while in motion will resemble adjacent threads of a double threaded screw and that each of these helices will have the same pitch and pitch angle.. Itwill be apparent also' that any other arbitrarily chosen circumferential strip o'f'rn'y improvedlpro- )eller blade obtained in the same manner will Athe surrounding water contigiions tothe blade is,A caused to have suchi'a relative motion to the propeller blade that it glides past the leading edge in the directionofsine such helixas indicated by the broken line-11,' and leaves the blade in the directinof some such helix as indicated by the'broken" 'line' 12,:andV

when the preferred vforni of my:- invention is used this 4relativeV niovementtakes place without shock and the `foilsequent v'loss offenergy caused thereby and also' without causing the water to receive the rotary `motion usual- 1y imposed by propellers of truegscrew form,V thus conserving the v'power lusuaflly 'lst in vproducing suchjrotary Vmotions fMy invention, therefore',` embodies-in `itself a Iieans for Ypreventingy the water passing through the.

propeller from having such arotating 'Inovement, and eliminates thecost of extraneous mechanism'` designed to redirect `the'-.revolving race for the purposev of recovering the power lost" inproducing' the-aforesaid rota` tion'of the race, andmy invention also eliminates the use of any mechanism 'extraneous'to the4 screw propeller whichY is designedV to prevent the aforesaid rotation of the'race.

-The blade forni,'as. hereinabove described, has .been treated as though it were a curved surface having' no thickness. Itiscontemplated, however, inther preferredy for'm; of my invention-td have the driving ifacebofthe plate, viz, the ,face shwnin Figs; 1fahd'i, coincidevvith the superficial formv above specified and tol dispose theimaterial thicknessof the 'blade at the rear of a1 driving' surfacefof thiskr configuration: It; will begunderstod,

however, thatrmanyvariations ,of'my inven-4 tion may be produced by disposing the thicknessof the blade partly'at the rear and partly'at the front of the outlinev or superficial form above speciiied,`while1still retaining the characteristics of 'said superficial Lform,

yand that the rear surface ofthe blademay have this form or a somewhatdiiferent form, l

vconvexity, however, being always disposed so that the concavity will-be adjacent to the leading edge and the convexity adjacent to the following edge ofthe blade.

The blade form, which has been described above by means of a representative strip or section can be readily comprehended as a whole by the following description of amechanical method of sweepingthe lsaid blade form. Thus, in Fig. 4 21 indicates a rodterminating in a boss 22, which boss is bored' so as to be able to slide and turn on apivotal rod 23.

Starting with the rod 21\ in the position' i X-X shown in said Fig. 4, it is vgiven a uniform clockwise angular motion and at the same time moved upwards, this upward motion'beginning with the velocity /v-but de'- creasing to another velocity 'v at the position Y-Y. The rod 21 is now replaced in'its i .i first position at X-X and thenmoved down- V"wards beginning with` the velocity v and 'terminates with the smaller velocity f/v p at Z-Z. During this downward motion the rod is rotated with a uniform counter-'clockwise 2. A-screw propeller `comprising; a plurality of blades, each Iprovided with. a driving facehaving a contour produced by connecti ing portions ofthe screw surfaces of two adjacent threads of a double-threaded screw of similar pitch by a transition' lsurface of concavo-convex curvature, they opposite ends of said transition surface being, respectively, f

tangential to the adjacent-threads ofsaid double-threaded screw.

3. A screw propeller comprising a plurality of blades, each provided with a driving 'face having a contour producedby connecting portions of the screw surfaces of two Vadjacent threads of a double-threaded screw of similar pitch by a transitionsurface of concavo-convex curvature, the concave portion of said concavo-convex curvaturel being arranged adjacent to the leading edge and the convex portion being arrangedEadjaCent to the following edge of said blade and the opposite ends of said transition surface being,

respectively, tangential tothe adjacentV threads of said double-threaded screw.

In witness whereof, I have signed my name tothe foregoing specification.

. j ATI-IDLE` J.

, angular velocity equal t0 the above clockwise velocity. During these upward andY downward motions the rrod 21 will trace out in space a surface' from which the blade can be .templated and cut out on the dotted contour shown projected in to the surface above formed. v

I-Iaving described my invention, I cla-im 1. A screwv propeller` for marine vessels having blades, each having a driving `face of substantially concavo-convex curvature across the said face, the concave and convex portions being of substantially similar curvaj .ture and pitch and the concave'portion being adjacentto the leading edge and the convex portion'adjacent to the followingedge, said Y bladeface also havinga helicoidal curvature and said surface being so arranged that the concave and convex-portions thereof will,.re

spectively, be substantially tangential duringrotation to helical paths. of motion that leachftravel relative to the surroundingme- 

